investigating Pitch oscillation when transitioning to hover

[104th_Money]

I am getting a non pilot induced pitch oscillation during hover transition. Pulling back on stick to flare and it starts rocking forward and back for a few seconds before it settles back down.

[NineLine]

Is this a custom mission or one supplied? Can you give us a track please?

[104th_Money]

This is a custom mission. I was able to recreate again but then I figured out that I didnt have all the autopilot channels turned on. It doesnt do it with them all on ...

 

Thanks

[KoN]

Your lucky I pull back to flare and flop into the ground  , . 

But its early days and early access . loving it though . 

[Jowen G. Bruère-Dawson]

Yep, I found that at some rotor pitch angles, the helo starts to oscillate in pitch

[Nealius]

I'm finding it to start oscillating at 130kph, rotor pitch at 5, descending 3m/s, aft cyclic. She settles out when decelerating through 100kph at the same rotor pitch. I have Roll and Pitch stability systems on when this occurs. 

[S. Low]

If you have a flight where you get pitch oscillation that you think is a bug, when you quit out of the mission save the track file and upload it with a time stamp.

[VampireNZ]

Also getting pitch oscillations when slowing on approach to land. Stabilized gentle slowdown/descent and it just starts nodding for no reason.

[BIGNEWY]

need to see track replays showing the problem please

[KoN]

The best landings  I've found is to land like a slow moving bird .

line up on runway and glide down slow ,  but don't go into a hover .

This works for me , I've seen many pilots trying to hover into a land and just flop out of the sky into the deck crash and burn . 

[Blackeye]

On 6/21/2021 at 10:18 AM, BIGNEWY said:

need to see track replays showing the problem please

 

Here's a track of it happening at around 130 kph - I tried to be very smooth and not make corrections during the oscillation and you can see the AP pitch channel starting to pitch up and down without stick input. Ignore the crappy landing part

demo2.trk

Edited June 23, 2021 by Blackeye

[Maverick24]

I can confirm this behavior. I can trim helicopter, hands off controls and it´s oscilating a few degrees up and down and it visible on AP pitch channel.

[yngvef]

I have seen it, but thought it was just a natural effect of transitioning from forward flight to hover flight. Just like the vibration in the Mi-8?

[Blackeye]

14 hours ago, yngvef said:

I have seen it, but thought it was just a natural effect of transitioning from forward flight to hover flight. Just like the vibration in the Mi-8?

 

It occurs at 130+ kph which is way above the transition speed from ETL to hover - those effects happen below 40-ish kph.

[leapingrodent]

I have also noticed this behaviour today.

[Nealius]

I'm still noticing this behavior when slowing down from around 150kph. Nose oscillates up and down while my physical and virtual sticks are stationary. Whatever is causing the pitch oscillations, it is not being caused by stick movements. AP channels on/off doesn't seem to make a difference. These are all custom missions with turbulence set to 20. For those who don't have oscillations, do your missions have any turbulence set?

[River]

Same for me, Aircraft starts pitching up and down at around 130 kmh during slow down. 

[IcedVenom]

You're probably going way too fast

[admiki]

Going too fast for what? AFAIK cruise speed is around 260 kph, so how is he going to avoid going 130 kph while slowing down for hover/land?

[Quati]

It happened to me also a couple dozen times. Yesterday I had twice on Rotorheads server.

When I'm decelerating slow through that velocity span 100-150km/h (never payed much attention to the exact values) I got those non-pilot induced oscillations in pitch because of that it's hard to get a beautiful and steady approach from cruise speed (~250km/h) to final approach speed (~80km/h) that way.

When you decelerate quickly trough that region that oscillation is not perceived.

It's like that is a transition speed that you should not be at for long time. Like a machine speed you should avoid that is close to the natural frequency of it or a transitional flow between laminar and turbulent you should avoid when design a fluid system.

[AeriaGloria]

I doubt it’s real behavior. It’s been marked as an issue before, and the oscillation has improved since release. 130 kmh is bucket speed, it’s the speed your are at for best climbing rate, best endurance, single engine out speed, your around 140-170 kmh for auto rotation/descent, I think it’s just an issue of the way the AP is tuned 

If you turn pitch AP off, issue goes away, so i doubt it’s turbulent air/transition flow 

7 hours ago, Quati said:

It happened to me also a couple dozen times. Yesterday I had twice on Rotorheads server.

When I'm decelerating slow through that velocity span 100-150km/h (never payed much attention to the exact values) I got those non-pilot induced oscillations in pitch because of that it's hard to get a beautiful and steady approach from cruise speed (~250km/h) to final approach speed (~80km/h) that way.

When you decelerate quickly trough that region that oscillation is not perceived.

It's like that is a transition speed that you should not be at for long time. Like a machine speed you should avoid that is close to the natural frequency of it or a transitional flow between laminar and turbulent you should avoid when design a fluid system.

 

Edited March 29, 2022 by AeriaGloria

[Quati]

14 hours ago, AeriaGloria said:

I doubt it’s real behavior. It’s been marked as an issue before, and the oscillation has improved since release. 130 kmh is bucket speed, it’s the speed your are at for best climbing rate, best endurance, single engine out speed, your around 140-170 kmh for auto rotation/descent, I think it’s just an issue of the way the AP is tuned 

If you turn pitch AP off, issue goes away, so i doubt it’s turbulent air/transition flow 

 

 

I agree with you.

I was just trying to to give examples to explain that in the DCS Hind, at the moment, you should avoid that speed region if you wanna fly steady (for a attack) or beautifully to show off your flying skills on a video when approaching. As a mechanical engineer those examples of "regions to avoid" came in my mind.

So, in the current state of the DCS Hind, when trying to snipe a target with the 30mm, or keep it steady for Petro engage a target with ATGM I would avoid getting in that speed region during a attack run.

As I do not have a good joystick with extension I rather avoid staying at that speed region than turning off the AP Pitch.

 

[AeriaGloria]

3 hours ago, Quati said:

I agree with you.

I was just trying to to give examples to explain that in the DCS Hind, at the moment, you should avoid that speed region if you wanna fly steady (for a attack) or beautifully to show off your flying skills on a video when approaching. As a mechanical engineer those examples of "regions to avoid" came in my mind.

So, in the current state of the DCS Hind, when trying to snipe a target with the 30mm, or keep it steady for Petro engage a target with ATGM I would avoid getting in that speed region during a attack run.

As I do not have a good joystick with extension I rather avoid staying at that speed region than turning off the AP Pitch.

 

Ah I see, I agree. I have a FFB sidewinder. So not only do I have no extension but I can’t use curves!!!! I think the inertia of the Mi-24 actually makes it easier to handle then the Ka-50 becuase of that